Heat-resisting object containing iron and aluminum



Patented Sept. 13,1938

UNITED STATES PATENT oer-"ice Werner Hessenbruch, Hanau-on-the-Main,

Germany i No Drawing. Application September 5, 1936, se-

rial No. 99,620. In Germany September 24,

- s Claims. 01. 148-1) This invention relates to objects made of an alloy containing iron and aluminum.

It is known to make electrical heating elements of alloys which, in addition to iron, contain various amounts of aluminum, for example 242% and may also contain chromium in amounts from 0.1 up to about 35%. These alloys are distinguished by the feature that, in general, they are very resistant to heat up to temperatures of J about 1,300 C. It is also known that these alloys sometimes exhibit an abnormal phenomenon which may be termed blistering (formation of carbuncles). This phenomenon consists in the formation at various places on the heating element for example of black spots, which then lead to accelerated oxidation and to breakage of the heating elements at these places. Reference has been made to this phenomenon for example in the periodical Elektrowarme, January 1935,

o in an article entitled Ueber hochhitzebestandige Chrom-Aluminium-Eisenlegierungen.

According to the present invention, the formation of these blisters or carbunclesand therefore premature local destruction of the heatingv 5 elements is avoided by treating the material with an alkaline solution before it is brought into operation. For example, the heating elements are placed in a sodium carbonate solution, in lime water, baryta. water or caustic soda solution. The duration of the immersion in the alkaline solution may amount, for example, to a few hours but may also be extended toseveral days.

If the material is then removed from the alkaline solution and the residues of the alkaline constituents are burnt in by heating to a temperature of several hundred degrees the afore-; mentioned tendency to form blisters is entirely re-' moved. The burning in of the alkali can be eifected either in a separate operation or when p the material is heated for use for the first time; u

1. The method of increasing the resistance to heat of objects made of a ferritic alloy containing iron and aluminum which method comprises subjecting the objects to the action of an alkaline solution of the group of sodium carbonate solution, lime water, baryta water, and caustic soda solution, removing the objects from the alkaline solution and drying in the remaining alkaline constituents.

2. The method of increasing the resistance to 5 heat of objects made of an alloy consisting of iron and aluminum, which method comprises subjecting the objects to the action of an alka-- line solution of the group ofsodium carbonate solution, lime water, baryta water, and -caustic soda solution, removing the objects from the alkaline solution and drying in the remaining alkaline constituents.

3. The method of increasing the resistance of heat of objects made of an alloy consisting of iron, aluminum and chromium, which method comprises subjecting the objects to the action of an alkaline solution of the group of sodium carbonate solution, lime water, baryta water, and caustic soda solution, removing the objects from the alkalinesolution and drying in the remaining alkaline constituents.

4. The method of increasing the resistance to heat of objects made of an alloy containing iron and aluminum, which method consists-in immersing the objects for a period of from several hoursto several days in an alkaline solution of the group of sodium carbonate solution, lime water, baryta water, and caustic soda solution,

removing the objects from the alkaline solution and drying in the remaining alkaline constituents. 5. The method of increasing the resistance to heat of objects made of an alloy containing iron. and aluminum, which method consists in immersing"the objects for'a period of from several lidurslto several-days in an alkaline solution of the ,'roup of sodium carbonate solution, lime water, baryta water, and caustic soda solution, and removing a deposit formed on the solution 40 before removing the objects from the solution. 6. The method of increasing the resistance-to heat of objects made of an alloy consisting of iron, aluminum and chromium which method consists in immersing the objects for a period of from several hours to several daysin an alkaline solution of the group of sodium carbonate solution, lime water, baryta water, and caustic soda solution, removing the objects from the alkaline solution and" drying in the remaining alkaline constituents. '1. The method of increasing the resistance to heat of objects made of an alloy consisting of iron, aluminum and chromium, which method consists in subjecting the objects to the action consists in immersing the objects for a period of from several hours to several days in an alkaline solution of the group of sodium carbonate solution, lime water, baryta water, and caustic soda solution, removing a deposit formed thereon, removing the objects from the solution, and drying in the remaining alkaline constituents.

WERNER HESSENBRUCH. 

